Palpebral (bone)

Palpebral bone (highlighted) of Heterodontosaurus

Palpebral bone (highlighted) of Pliosaurus

The palpebral bone is a small dermal bone found in the region of the eye socket in a variety of animals, including crocodilians and ornithischian dinosaurs. In ornithischians, it can form a prong that projects from the front upper corner of the orbit. It is large in heterodontosaurids,^[1] basal ornithopods such as Thescelosaurus (as Bugenasaura) and Dryosaurus,^[1][2] and basal ceratopsians such as Archaeoceratops;^[3] in these animals, the prong is elongate and would have stuck out and over the eye like a bony eyebrow. As paleoartist Gregory S. Paul has noted, elongate palpebrals would have given their owners fierce-looking "eagle eyes".^[4] In such cases, the expanded palpebral may have functioned to shade the eye.^[5]

References

1. Norman, David B.; Sues, Hans-Dieter; Witmer, Larry M.; Coria, Rodolfo A. (2004). "Basal Ornithopoda". In Weishampel, David B.; Dodson, Peter; Osmólska, Halszka. The Dinosauria (2nd ed.). Berkeley: University of California Press. pp. 393–412. ISBN 0-520-24209-2.
2. Sues, Hans-Dieter; Norman, David B. (1990). "Hypsilophodontidae, Tenontosaurus, Dryosauridae". In Weishampel, David B.; Osmólska, Halszka; Dodson, Peter. The Dinosauria (1st ed.). Berkeley: University of California Press. pp. 498–509. ISBN 0-520-06727-4.
3. You Hailu and Dodson, Peter. (2004). Basal Ceratopsia. In: Weishampel, David B.; Dodson, Peter; and Osmolska, Halszka (eds.) The Dinosauria (2nd Edition). Berkeley: University of California Press. p. 478–493.
4. Paul, Gregory S. (2000). "Restoring the Life Appearances of Dinosaurs". In Paul, Gregory S. The Scientific American Book of Dinosaurs. New York: St. Martin's Press. p. 102. ISBN 0-312-26226-4.
5. Naish, Darren; David M. Martill (2001). "Ornithopod dinosaurs". Dinosaurs of the Isle of Wight. London: The Palaeontological Association. p. 79. ISBN 0-901702-72-2.